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Nov 16, 2012: Cladina stellaris and Stereocaulon tomentosum

Cladina stellaris and Stereocaulon tomentosum

Bryant is the author of today's entry:

I would like to thank Richard Droker (aka wanderflechten@Flickr) for this image of a lichen community near White Pass, Yukon. The highly branched/shrub-like species of lichen towards the upper half of the image is Cladina stellaris (formerly Cladonia stellaris) and the more coral-like species occupying much of the lower third of the image is Stereocaulon tomentosum. The vascular plant is crowberry, or Empetrum nigrum. If you think that this image looks like a miniature forest, you are not the only one. A major economic use of Cladina stellaris is for miniature trees on small scale models by hobbyists and architects alike.

Lichen communities like this one can dominate a local environment. Often forming dense mats, lichen communities can out-compete plant species for real estate by preventing seedlings from establishing themselves. Seedlings that do manage to take root may be pulled out or damaged by the repeated swelling and contracting of the lichen with changes in moisture. Lichen communities can also affect the underlying soil systems by regulating soil nutrients, retaining soil moisture, and maintaining microbiological communities.

Cladina stellaris (commonly known as star-tipped reindeer lichen) often forms large and rather dense mats in its widely distributed range. As its common name suggests, it is a major source of food for both reindeer and caribou, especially in the winter. Cladina stellaris contains the liver-toxic substance usnic acid, used in products like perfumes and antibiotics. Usnic acid has a bitter taste, which has deterred indigenous peoples from eating raw lichens. However, reindeer and caribou can tolerate the acid with the aid of rumen microorganisms. It has even been proposed that usnic acid aids in digestion by reindeer because it can be successfully metabolised by the rumen microbes. Indigenous peoples discovered that the partially digested lichen found in the first stomachs of reindeer and caribou can indeed be eaten, as the usnic acid has been broken down.

Stereocaulon tomentosum is a woolly lichen with rounded gall-like growths that contain blue-green algae. Richard has also taken a close-up image of the woolly hyphae and gall structures.

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